


On Knife's Point

by gaylie



Category: Underfell - Fandom, Undertale (Video Game)
Genre: Blindfolds, Bondage (Handcuffs), Fontcest, Knife Play, M/M, Underfell AU
Language: English
Status: Completed
Published: 2016-08-29
Updated: 2016-08-29
Packaged: 2018-08-11 16:45:30
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 2,372
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7900312
Author URL: https://archiveofourown.org/users/gaylie/pseuds/gaylie
Summary: <blockquote class="userstuff">
              <p><i>Sans couldn't move his hands when he woke up.</i><br/><i>It wasn't the only thing Sans noticed either. When he tried to open his eyes, for a second he thought he'd gone blind. But he could see. Just foggy, faint light through the blindfold that he realized was around his face.</i><br/> </p>
<p>In which boss decides it's time to teach Sans a bit of a lesson again.</p>
            </blockquote>





	On Knife's Point

**Author's Note:**

> so a friend of mine is rly into knife play so lets just say this fic is lowkey for her
> 
> first time writing knife play, or even BDSM stuff like that, i'm surprised how easily i got into it??

Sans couldn't move his hands when he woke up.

Or, well, he could, but they were connected to one of the bars of the headboard of their fancy, way-too-expensive bed, with a pair of handcuffs. His wrists were placed above his head, and the best he could do was wiggle them left and right by a few centimeter.

It wasn't the only thing Sans noticed either. When he tried to open his eyes, for a second he thought he'd gone blind. But he _could_ see. Just foggy, faint light  through the blindfold that he realized was around his face.

He wasn't sure what had caused it this time. He hadn't been awake for when boss locked him to the bed. Had he fucked something up? Was boss in heat? Or just in the mood? Maybe Sans had been screaming and thrashing in his sleep again and boss got fed up with it.

He knew, though, that struggling and fighting wasn't going to help him out of this situation. By the sound of it boss wasn't in the room right now either. Unless, if he was, he had to be extremely silent. And Sans was almost certain that his brother would've let out _some_ sort of amused chuckle by the way he had panicked at first. So chances were good that Sans was alone so far.

Those suspicions got confirmed once he could hear the clicking of heels from outside the room. Thanks to their father's success as Royal Scientists, the brothers had always lived rich, and in the large, empty halls of their mansion, the clicking of Papyrus' heels echoed widely.  Already that was enough to make Sans shiver in fear and excitement.

He couldn't quite make out from how far away the noise was coming from, so he simply had to wait. And his patience got rewarded with the noise of the door creaking open only seconds later. He took a sharp breath in anticipation.

The clicking of heels stopped, once boss entered the carpeted room, so the only noise Sans could hear was the faint swishing of fabric against fabric now and then. He didn't expect the  way the mattress moved a little as a new weight added on it.

“Slept well, brother?” His voice was hot and breathy against Sans' skull.

“heh, like a stone. gotta admit, though-” He gave a light tug at the handcuffs, the chain tingling a little. “-this was, _hands down,_ the best way to wake up.”

His laugh was weak and raspy, because he knew his brother wouldn't respond to the joke at all. Wasn 't a good one anyway.

“Is that so?” Papyrus asked, his voice not as close anymore than before, but still close enough to sent a shiver down Sans' spine. “Well, consider yourself lucky then, because this sure isn't all I've had planned for today.”  
Already Sans had trouble keeping his composure, but he tried his best to cover it up. “oh yea? heh, what's the occasion, boss?”  
“Oh, I thought you've been especially naughty lately,” the taller skeleton drawled, and Sans could feel him gently straddling him. He hadn't noticed before, but the way Sans woke up, he was still wearing some clothes. Not his trademark jacket, but thanks to the pressure now, he noticed the shorts he had still on, and shifting a little he could also feel a shirt. Peculiar. He had thought boss would've stripped him naked, if he was already handcuffing him to the bed.

Sans couldn't see it himself, but boss was already smirking a little to himself.  “I figured it might be time to teach you a bit of a lesson.  Remember your safeword? ”

S ans nodded a little, almost immediately interrupted by something touching his spine, just above where his tailbone started. He sucked in a sharp breath.  The tip of something thin and pointy found its way underneath Sans' shirt, gently moving it up as it slid along the vertebrae of his spine. For a moment Sans thought it was Papyrus' skeletal finger, thin and long with sharpened claws. But no. It was too cold for that. And then Papyrus turned the object a little, so that the edge of it was pressing lightly into Sans. Not enough just yet to hurt or damage him, but enough for Sans to tell that it was  _a knife._ Well, that was a first.

“f-fuck,” he gasped, a bit overwhelmed. “you s-sure are one _sick_ fucker, arentcha?”  
“ Watch your mouth, brat,” Papyrus scolded, moving the knife up to press the blade underneath Sans' chin. Just enough pressure to lift the skeletons head a bit, point pressing lightly into where his windpipe would be. “You wouldn't want to get seriously hurt, now would you?”

“ _fuck_ you!” Sans spat, actually spitting into the general direction where Papyrus' voice came from. He was grinning, although not sure whether he missed or not, but that grin got wiped out of his face quickly enough anyway. Gasping, Sans could feel the blade pressing stronger against his throat, still not enough to cut him.

H e knew Papyrus loved it when he fought. Because you couldn't punish someone who'd be just obedient all the time, could you? And it was no secret that  _punishing_ was what Papyrus loved doing the most.

And there was always something exciting for Sans, to see boss getting agitated over his struggling, fighting, his biting remarks. He would submit to Papyrus in the end anyways, always, but where would be the fun if he'd just do it right away?

“Don't pretend like you're not into this. I can see the way you're already panting.” He slowly, strongly rolled his hips against Sans, grinding their pelvises together. It forced a choked out moan out of Sans. “You've been aroused since the moment you woke up.”  
The smaller let out a hollow, breathy laugh as he wiggled his pelvis a little against his brother's.

“you're one to talk.” He grinned up at boss. “'s not like i can't feel your rock hard bulge against my shorts.”

W ith a single, swift motion  Papyrus moved the blade from under Sans' chin  over his cheek, this time leaving a fine cut, almost reaching up to his eye socket. It surprised him,  _scared_ him more than it actually hurt, but either way, he let out an ear shattering scream, feeling tears gather up underneath the blindfold.

“fuck! fuck, _damn it,_ ” he cursed through grit teeth, chain rattling as he tried to pull his hands towards the cut on his cheek.

“I _told_ you to fucking watch your mouth,” Papyrus growled, and even through his blindfold, Sans could easily picture the menacing smile on his brothers face.

“ _asshole_ ,” he hissed, still thrashing with his arms. “fucking _psychopath_!”  
With an ease that scared Sans, Papyrus stilled him by holding both of the smaller's wrists down with one hand. He tutted a few times and Sans could hear his long claws sliding over the knife's blade, currently held far away from Sans' body, that he couldn't tell where exactly it was. He swallowed hard.

“Stop whining already, you vermin. I _know_ you Sans. This is hardly _anything_.”  
Sans scoffed, but couldn't disagree either. The stinging of the cut was _far_ from his limit.  The pain and shock merely sent his heart racing, stomach churning in excitement. And after all, he knew the safeword.

Making sure that Sans had calmed down again, Papyrus released his wrists from his hold and brought the knife back in action. Sans' shirt was already moved up far enough that it was lying around where his sternum started. With a far too slow motion Papyrus moved the edge of the knife along it, along Sans' sternum, cutting through the fabric in the progress. Sans couldn't help but to squirm and whimper as the sensation and pain dragged on for _too_ long. Papyrus had only pressed on the bone strong enough that it left tiny cuts here and there. But the shirt was almost cut entirely through from bottom to the top, definitely enough for Papyrus to quickly rip it off.

Sans gasped startled, but almost immediately he could feel boss' warm, gloved fingers stroking over his exposed ribs, and his gasp quickly turned into a blubbered moan.  He didn't notice Papyrus'  face getting closer to his' until he could feel the hot breath against his teeth.  Almost instinctively he parted them, letting the other's thick tongue in.  Quickly Sans summoned his own, wrestling with the invading tongue for dominance for a bit,  before finally letting him roam through the inside of his mouth freely.  Like this, he could almost forget the knife that was now lying somewhere in Papyrus hand, away from Sans' body. He cherished the taste of Papyrus' tongue, sucking and nibbling on it only a little bit, not enough to anger him. Sans hated a little how much louder he always was than boss, already becoming a moaning mess underneath him. 

When boss finally moved his face away again, Sans followed as far as he could, which wasn't very far thanks to being chained on the bed, a small needy whine escaping his lips.

“God, you're such a slut, Sans,” Papyrus hummed deeply. He dragged the knife gently over Sans' rips, the clicking sound of steel hitting bone almost louder than Sans' panting. “I bet this is already making you so wet.”  
Oh, he had _no_ idea.

“c'mon b- _hah-_ boss,” Sans breathed out through his pants. “just _fuck me already!_ ” As if to emphasize his words, he gave a strong thrust against the bulge in Papyrus' pants, actually earning himself a surprised groan.  
Which quickly turned into a deep, collected laugh.

“You want it _that bad_ , don't you?” The taller skeleton purred, removing Sans' shorts almost too gently. The sudden cold on his already formed pussy made Sans shiver a little, groaning through his teeth.

“Well why don't you _beg_ for it then, hmm?”  Despite his words, Sans could hear the noise of Papyrus undoing his belt. Or maybe exactly _because_ of his  words, because the sound just made Sans feel even needier to just be filled.

“I'm waiting.” Papyrus cooed, slowly repositioning himself on Sans lap. He didn't push in yet, still waiting for Sans to beg, but Sans could feel the hot _presence_ of Papyrus' cock so close to his entrance. He couldn't help but to let out a wanton whine.

“p-please boss,” he whispered. “fuck me. fucking _wreck me._ ”

P leased, boss chuckled deeply. “Oh well, since you asked so nicely.”  
With one, powerful thrust he pushed his entire length in, filling Sans completely. He didn't waste a second either, immediately starting to thrust.  
“ooooooh _fuck yes,_ ” Sans groaned, moving his hips to meet Papyrus' thrusts.  
Finally boss seemed to become undone, too, panting and moaning in tandem with Sans underneath him.  He could hear him shift until his head was flush against the sensitive bone between Sans' shoulders and neck vert e brae. Idly Papyrus continued stroking the rib s with the edge of the knife, leaving more and more scratches and cuts on them.   
The more often the blade ran over the cuts, they wider they opened and the more jolts of pain they sent over Sans' body, right to his core, leaving him a writhing, moaning mess.  He leaned into every one of Papyrus' touches, met every one of his thrusts. And once he felt boss' tongue sliding along the ridges of his vertebrae, Sans knew he was close.

His walls were already tightening around  Papyrus' cock, warning the taller of just that.

“Don't you dare. Cum. Until I. Say so,” he huffed, emphasizing his words with stronger thrusts. “Do you understand, _mutt?_ ”  
Sans couldn't form any coherent words, his mind swimming in too much pain and pleasure, but Papyrus quickly brought him back to reality, with another strong slash of his knife. This time over Sans' sternum, hot blood already running and dripping down his ribs, as Sans' shriek died down.

“I said. _Do you understand?_ ” He repeated, louder, slower this time.

“y-yes, yes boss, yes,” Sans blubbered in between his cries and moans. There were more tears now gathering in his eyes, moistening the blindfold, making it stick grossly around Sans' eye sockets. He literally couldn't care less right now. Instead all of his willpower and focus went into trying not to cum before boss gave him the go.

Blessedly he didn't have to wait too long. Only a few thrusts later, Papyrus breathing got erratic and his thrusts lost rhythm, got stronger, faster,  _wilder._ Sans could tell he was close.

“Come now,” Papyrus breathed, teeth still against the nape of Sans' neck. “Come for me.”  
And that was more than enough to push Sans over the edge, crying out loudly as he did so. Seconds later he could feel boss coming too, filling him even more, while biting deep into Sans' bone. His teeth almost hurt more than any of the cuts did.

Panting, he slowly rode out both of their orgasms, before pulling out of Sans. Sans himself didn't move, still bound to the bed and blindfolded. But even if he hadn't been, Sans never was one to move a lot after an orgasm, often just falling straight asleep.

He heard Papyrus' belt clinking, as he presumably put his pants back on, before the taller skeleton shifted to sit next to Sans on the bed. Gently he undid the handcuffs and pulled the smaller monster on his lap.

“heh, you're even more of a freak than i thought,” Sans chuckled, his voice low and breathy.

“Speak for yourself,” his brother answered nonchalantly. He removed the blindfold slowly, leading Sans' face to look up at him. It took Sans a little to get used to the light again, blinking a few times, but once he did he was met with a stoic expression.

“I hope I didn't hurt you too much. You're delicate.”  
A gloved finger trailed along the series of cuts and scratches along his ribs, and almost shyly tracing along the edges of the big cut on his sternum. Sans let out a breathy laugh.  
“oh come on, boss. this ain't nothing.”


End file.
